An Arizona-based advocacy group is accusing US Border Patrol of using the desert's harsh terrain as a ‘weapon'

File photo of a U.S. Border Patrol Agent patrolling along the U.S. and Mexico border in Naco Arizona Thomson Reuters

The US Border Patrol agency has engineered the death and disappearance of tens of thousands of undocumented immigrants by using the desert wilderness as a "weapon", according to an advocacy group.

Agents chase and scatter border crossers across hostile terrain in a strategy that leaves many people injured, dead or lost, turning the US's south-western frontier into a "vast graveyard of the missing", the Arizona-based group No More Deaths said on Wednesday.

"The known disappearance of thousands of people in the remote wilderness of the US-Mexico border zone marks one of the great historical crimes of our day," the group said in a blistering report, the first of three reports documenting alleged abuses by Border Patrol.

In addition to deadly apprehension methods it accused the federal agency, which deploys about 18,000 agents on the 2,000-mile border with Mexico, of sabotaging humanitarian aid efforts and discriminating against undocumented people in emergency responses.

No More Deaths, a ministry of the Unitarian Universalist Church of Tucson, worked with volunteers from another group, La Coalición de Derechos Humanos, on the 34-page report. It drew on a survey of 58 border crossers and 544 cases from the Missing Migrant Crisis Line. Tens of thousands have gone missing since the 1990s, including 1,200 last year, it said.

"If found, the disappeared turn up in detention centers, in morgues or skeletonized on the desert floor; many human remains are never identified. Thousands more are never located. With each passing day, another father, sister, aunt, brother, partner or child goes missing while attempting to cross the Southwest border."

A boy looks at a fence that is part of a section of the U.S.-Mexico border wall at Sunland Park, U.S. opposite the Mexican border city of Ciudad Juarez, Mexico, September 9, 2016. Picture taken from the Mexico side of the U.S.-Mexico border. Reuters/Jose Luis Gonzalez

"CBP values human life, and we collaborate closely with foreign government officials, law enforcement partners, and community organizations to educate potential migrants about the true dangers of crossing the border illegally."

The agency blamed deaths on smugglers. "Smugglers lie, telling their 'customers' their passage will be safe, but in reality, the terrain is treacherous and the conditions are extreme. Many are led to their deaths by smugglers more concerned about making money than they are about the lives of others."

Donald Trump has promised to wall off the southern border to stop undocumented immigrants and illegal drugs entering the US, raising expectations of an expanded border force and intensified interception efforts after he becomes president next month.

The National Border Patrol Council, a union which represents agents, has endorsed Trump's candidacy and advised his transition team. It says about half of border crossers slip through, a "frightening" security gap which leaves the US vulnerable to drug cartels and terrorists.

Central American migrants stand atop wagons while waiting for the freight train "La Bestia", or the Beast, to travel to north Mexico to reach and cross the U.S. border, in Arriaga in the state of Chiapas January 10, 2012. REUTERS/Jorge Luis Plata/File Photo

Border manpower and hardware has increased exponentially since 9/11, transforming what was a chain link fence into a zone bristling with cameras, sensors, drones and rapid response teams.

No More Deaths depicts the border as a gauntlet which often condemns would-be crossers to grim and uncertain fates. It said the policy was rooted in a 1994 Clinton-era Border Patrol strategy called "Prevention Through Deterrence" which sealed off urban entry points and funneled people to wilderness routes risking injury, dehydration, heat stroke, exhaustion and hypothermia.

The Border Patrol estimates at least 6,000 have died since the 1990s. Other estimates are significantly higher. With many bodies never found, precision is impossible.

The report accused agents of hounding people to injury and death, and brutalising those they captured: "Mass death and disappearance are the inevitable outcomes of a border enforcement plan that uses the wilderness as a weapon."

Of the 58 border crossers who were interviewed, 47 said they had been chased within the past five years, some several times. "We run as if we were blind, as if we had a cloth over our eyes," said one.

The report cited the case of a 29-year-old Salvadorean who went missing on 27 August 2015 after fleeing a patrol in south Texas. He told his family in a text message he thought his foot was broken. His whereabouts and fate remain unknown.

Mexican immigration officers talk with a man whom they suspect to be an illegal immigrant during a search operation in Zapopan near Guadalajara, Mexico July 29, 2014. REUTERS/Alejandro Acosta/File Photo

Pursuit increases the risk of dehydration, heat stroke, exhaustion, injury and drowning, the report said. And more than 40% of chases, according to the survey, resulted in someone becoming lost.

A mother told the Missing Migrant Crisis Line in August 2015 that she received a text from her son saying he was lost in Arizona's Ajo region. "He said 'migración' had made his group scatter, and that he was alone, having lost sight of his group when everyone ran." His fate remains unknown.

Of the 67 chases, 12 resulted in injury from excessive force during apprehension, according to the survey. The report cited cases of people being punched, kneed, hit with vehicles, intimidated and bitten by dogs. Border Patrol agents have killed 48 people since 2010, half of them during pursuit, it said.

The next two reports will detail allegations that agents have vandalised humanitarian supplies - Samaritans and other groups leave food and water on trails - and discriminate against undocumented people in emergency response.

Minutemen-like militias claim Border Patrol efforts are an Obama administration sham and that the frontier is open, a de facto welcome mat for "criminals" and "aliens".

"Everybody knows where the checkpoints are. It's window dressing," said Harry Hughes, who said he had just returned from the field, monitoring cartel scouts. He doubted Trump would change much. "Congress writes the checks."

Getty Images/John Moore

Robert Crooks, another Arizona Minuteman, was more bullish and said Trump was already having an impact. "A lot of the illegals have already started self-deporting because they know a change is coming."

Would-be crossers at immigrant shelters in Nogales, just inside Mexico, called the border a formidable barrier with treacherous terrain and ubiquitous cameras, sensors, drones and patrols, real or perceived.

To cross they must pay several thousand dollars in fees and "taxes" to criminals, or haul drugs. Being spotted by Border Patrol can mean forfeiting a fortune or going to jail for drug smuggling. Either way, a strong incentive to flee.

The risk of getting lost in the wilderness are set against the certain grimness of being shackled and herded back into Mexico, broke, desperate and, in the case of those in Nogales, cold.

Some deportees sleep in a cemetery, huddling under blankets, branches and cardboard to survive sub-zero temperatures.

"My mother prays for me," said Betancourt, a Honduran. Deported last March after a decade in the US, he had spent two months and several hundred dollars traversing 2,500 miles from Honduras up to Nogales. Now the US was a two-minute walk away. From some tombstones you could see the 18ft steel border fence.

Betancourt declined to reveal his full name, or how he intended to cross. But if spotted by Border Patrol he had a plan: "Run."